This invention is generally directed to imaging members and processes for the preparation thereof. More specifically, the present invention relates to layered photoconductive imaging members with excellent mechanical characteristics, and which members contain high molecular weight and narrow dispersity polymers. In embodiments, the present invention is directed to the fabrication of photogenerating layers by the in situ polymerization of mixtures of macrocyclic oligomers and photogenerating pigments. The aforementioned photoresponsive imaging members can be negatively charged when the photogenerating layer is situated between the charge transport layer and the substrate, or positively charged when the charge transport layer is situated between the photogenerating layer and the supporting substrate. The layered photoconductive imaging members can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein negatively charged or positively charged images are rendered visible with toner compositions of the appropriate charge. Generally, the imaging members are sensitive in the wavelength regions of from about 400 to about 850 nanometers, thus diode lasers can be selected as the light sources in some instances.
Imaging members are usually prepared by first providing on a supporting substrate a photogenerating layer of, for example, trigonal selenium in a polymer binder. Photogenerating pigments are usually milled in an organic solvent to obtain a small particle size and certain morphology. The polymer binder is chosen with consideration of the aforementioned milling; phthalocyanine pigments, for example, are often converted to less sensitive morphologies by chlorinated solvents, and thus, the use of polymers that are only soluble in these solvents such as polycarbonate is normally precluded. Yet, polycarbonate because of its clarity and toughness is otherwise an acceptable polymer binder. This invention provides in embodiments the use of polycarbonate as a binder for photogenerating pigments since, for example, the cruical milling step takes place in the presence of a mixture of macrocylic carbonate oligomers rather than a high molecular weight polymer. The oligomer mixture is soluble in a wide variety of organic materials, and addition, needs not be dissolved at all since it is friable and can be broken down into small particles and widely dispersed among the pigment particles by milling. Conversion to high molecular weight polymer takes place after the solvent has been removed. Alternatively, coating may take place in the absence of solvent using powder coating methods. This invention in embodiments allows one to effectively prepare charge generation layers comprised of a polycarbonate binder and charge generating pigments. With the invention of the present application, in embodiments there is selected a mixture of macrocyclic carbonate oligomers and this mixture is converted into a polymer after or simultaneously with the coating of the charge generation layer. The advantages of the aforementioned include the provision of polycarbonate as a binder for pigments that are sensitive to chlorinated solvents. The processes of the present invention and imaging members thereof allows the charge generation binder to be optionally crosslinked to provide tougher coatings. Also provided are higher 100,000 to 300,000 polycarbonate films or polymers versus about 40,000 for spray coated molecular weight films formed using spray or dip coating techniques achieved with a polymer solution. The use of a solvent for forming a photoreceptor film may be avoided entirely with the present invention in embodiments by coating the cyclic oligomers and charge generation pigment mixture as a melt or a powder before curing the cyclic oligomers to obtain high molecular weight polymers. Additionally, by using mixtures of different structured cyclic oligomers high molecular weight copolymers of exact stoichiometry can be obtained that are not readily obtained by either the known interfacial or melt transesterification processes for producing polycarbonates.
Layered imaging members with photogenerating and charge transport layers, including charge transport layers comprised of aryl diamines dispersed in polycarbonates, like MAKROLON.RTM. are known, reference for example U.S. Pat. No. 4,265,900, the disclosure of which is totally incorporated herein by reference. More specifically in U.S. Pat. No. 4,265,900 there is illustrated an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer comprised of amine molecules dispersed in a polycarbonate. Examples of photogenerating layer components include trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, and metal free phthalocyanines. Additionally, there is described in U.S. Pat. No. 3,121,006 a composite xerographic photoconductive member comprised of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in the '006 patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles.
Photoresponsive imaging members with squaraine photogenerating pigments are also known, reference U.S. Pat. No. 4,415,639. In this patent there is illustrated a photoresponsive imaging member with a substrate, a hole blocking layer, an optional adhesive interface layer, an organic photogenerating layer, a photoconductive composition capable of enhancing or reducing the intrinsic properties of the photogenerating layer, and a hole transport layer dispersed in resin binders like polycarbonates. As photoconductive compositions for the aforementioned members, there can be selected various squaraine pigments, including hydroxy squaraine compositions. Moreover, there are disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxy squaraine compositions.
The use of selected perylene pigments as photoconductive substances is also known. There is thus described in Hoechst European Patent Publication 0040402, DE3019326, filed May 21, 1980, the use of N,N'-disubstituted perylene-3,4,9,10-tetracarboxyldiimide pigments as photoconductive substances. Specifically, there is, for example, disclosed in this publication N,N'-bis(3-methoxypropyl)perylene-3,4,9,10-tetracarboxyldiimide dual layered negatively charged photoreceptors with improved spectral response in the wavelength region of 400 to 700 nanometers. A similar disclosure is revealed in Ernst Gunther Schlosser, Journal of Applied Photographic Engineering, Vol. 4, No. 3, page 118 (1978). There are also disclosed in U.S. Pat. No. 3,871,882 photoconductive substances comprised of specific perylene-3,4,9,10-tetracarboxylic acid derivative dyestuffs. In accordance with the teachings of this patent, the photoconductive layer is preferably formed by vapor depositing the dyestuff in a vacuum. Further, there is disclosed in this patent dual layer photoreceptors with perylene-3,4,9,10-tetracarboxylic acid diimide derivatives, which have spectral response in the wavelength region of from 400 to 600 nanometers. Also, in U.S. Pat. No. 4,555,463, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with a chloroindium phthalocyanine photogenerating layer. In U.S. Pat. No. 4,587,189, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with a perylene (BZP) pigment photogenerating component. Both of the aforementioned patents disclose an aryl amine component as a hole transport layer, and resin binders like polycarbonates.
Moreover, there are disclosed in U.S. Pat. No. 4,419,427 electrographic recording mediums with a photosemiconductive double layer comprised of a first layer containing charge carrier perylene diimide dyes, and a second layer with one or more compounds which are charge transporting materials when exposed to light, reference the disclosure in column 2, beginning at line 20.
In copending application U.S. Ser. No. 537,714 (D/90087), the disclosure of which is totally incorporated herein by reference, there are illustrated photoresponsive imaging members with photogenerating titanyl phthalocyanine layers prepared by vacuum deposition. It is indicated in this copending application that the imaging members comprised of the vacuum deposited titanyl phthalocyanines and aryl amine hole transporting compounds dispersed in resin binders like polycarbonates exhibit superior xerographic performance as low dark decay characteristics result and higher photosensitivity is generated, particularly in comparison to several prior art imaging members prepared by solution coating or spray coating, reference for example U.S. Pat. No. 4,429,029.
In copending patent application U.S. Ser. No. 905,697 (D/92090) filed Jun. 29, 1992, there is illustrated, for example, a process for the preparation of photoconductive imaging members which comprises coating a supporting substrate with a photogenerator layer comprised of photogenerating pigments, and subsequently applying to the photogenerating layer a mixture comprised of charge transport molecules and cyclic oligomers, and wherein said mixture is heated to obtain a polycarbonate resin binder from said cyclic oligomers.
The disclosures of all of the aformentioned publications, laid open applications, copending applications and patents are totally incorporated herein by reference.